Tiredness and age.

[ian]

Don't know about anyone else but I have suddenly become aware that i can no longer do more than one full hard days work.

I simply have to take a full day to recuperate the following day!!

Bloody annoying!!

So you have discovered that what used to take a day now takes 2.
take a leaf out of Linus Pauling's book. It's not what you accomplish in a day, it's what you do. Linus set himself the target of walking for at least one hour each day. In his 94th year, Linus's daily walk might have been not much further than to and from his mail box, but he still achieved it.

[AlexS]

I've found that what I used to do all night now takes me all night to do.